Worm gear



FIG. 1 is a top plan view of a worm gear showing my new design;

FIG. 2 is a rear elevational view thereof, taken from the top of FIG. 1;

FIG. 3 is a front elevational view thereof, taken from the bottom of FIG. 1;

FIG. 4 is a side elevational view taken from the right of FIG. 1;

FIG. 5 is a bottom plan view thereof. 

The ornamental design for a worm gear, substantially as shown and described. 